ELIAHU BEN ELISSAR, chief of the Israeli delegation to the Cairo conference, is director general of the prime minister's office and was almost unknown in Israel before the upset election victory of Menahem Begin last May.

A tall, intropective man with a neatly trimmed black beard, Ben Elissar won his way into Begin's confidence by his ideological affinity to Begin's views and his thoughts, behind-the-scenes work during the years when Begin was in political opposition. He was in charge of press relations during the last election.

As far as is known, Ben Elissar has never been in Egypt, but for 10 years he served as an agent for the Mossad, the Israeli secret service, and was deeply involved with clandestine activities against Arab countries.

He was born Eliahu Gottleib in Random, Poland, in 1932 and like many Israelis he changed his name upon coming to Palestine. His father died in a concentration camp and his mother died in a road accident trying to reach what was then British Palestine.

He himself managed to escape from the Random ghetto by mixing in with the Christian funeral procession as it passed by the ghetto walls. He was adopted by a Jewish woman who was allowed to leave Nazi-occupied Europe in 1942 under an exchange of civilians between the British and Germans.

He was recruited by the Mossed while a student at the Sorbonne in Paris.

MEIR ROSENNE, also a graduate of the Sorbonne, is the Foreign Ministry's legal adviser and has been involved actively in all the Israeli-Arab negotiations since the 1973 war. He was the only civilian involved with the Egyptian-Israeli talks at Kilometer 101 right after the 1973 war. He was also involved with the disengagement negotiations with Syria, the Sinai withdrawals and was a member of the Israeli delegation to the 1973 Geneva conference. He comes to Cairo as the Israeli delegation's lawyer and he is known for his almost total recall of all the intricate legal points in the various documents concerning negotiations during the past four years.

MAJ. GEN. AVRAHAM TAMIK, a stocky, short man in his mid-50s, is known to all as "Abrasha," the Russian dinunative of his name. One of the most senior officers in the Israeli service, he won acclaim for a battle against Jordan's Arab Legion near Hebroa in the 1948 war. For many years he has been a defense planning specialist and in recent years was head of long-range planning. He brings with him to Cairo the results of a project he recently headed in which military and civilian analysts projected the probable effects on Israel of various peace alternatives.